Device for off-centering above-water articulated multiple-drilling structures

ABSTRACT

A device for off-centering an above-water articulated drilling structure in relation to a base on the seabed, consisting of a roller-table on the base, surmounted by a vertical pivot-shaft, a circular roller-path, also on the base and concentric with the pivot, an off-centering carriage that can revolve round the pivot, supported by the roller-table and roller-path, and with a guide-ramp along which the lower end of the main articulation of the structure can slide, and means for rotating the carriage and sliding the articulated structure along the guide-ramp.

United States Patent 1191 DeChassy et al. 1 Feb. 5, 1974 1 DEVICE FOR OFF-CENTERING 3,451,493 6/1969 Storm 17s/ss x ov w ARTICULATED 3,504,740 4/1970 Manning 166/.5 3,618,661 11/1971 Peterman.... 166/.5 MULTIPLE-DRILLING STRUCTURES 3,638,720 2/1972 Thomas 166/.5 [75] Inventors: Christian DeChassy, Gelos; Andre 3,667,240 6/1972 Vilain 61146.5

Capdeboscq, J urancon, both of France Primary Examiner-Wemer H. Schroeder Asslgneei EntrePllse De Recherches Attorney, Agent, or Firm-Joseph F. Brisebois et al.

DActivites Petrolieres (ELF), Pans, France [21] Appl. No.: 230,918

A device for oiT-centering an above-water articulated drilling structure in relation to a base on the seabed, [30] Foreign Apphcauon Pmmty Data consisting of a roller-table on the base, surmounted by M81. 5, 1971 France a vertical pivobshaft a circular roller.path also on the base and concentric with the pivot, an off-centering U-S- carriage that can revolve round the pivot upported the roller table and rolle zpath and a guide- Fleld of Search .6, 52, ramp along the lower end of the main articula- 175/7, 8, 9, 61/46, 46-5, 81 tion of the structure can slide, and means for rotating the carriage and sliding the articulated structure along [5 6] References Cited the guide-ramp.

UNITED STATES PATENTS 3,328,969 7/1967 Murphy et al. 175/9 X 9 Claims, 3 Drawing Figures DEVICE FOR OFF -CENTERING ABOVE-WATER ARTICULATED MULTIPLE-DRILLING STRUCTURES This invention concerns an off-centering device which fits between the lower end of an above-water articulated structure for drilling or oil production at sea, and a base resting on the seabed, allowing the structure to revolve or move transversely.

Existing above-water articulated structures, for under-water drilling or exploitation of under-water hydrocarbon deposits, are of the hull or trellis type, with floats possibly incorporated in the upper end. They are attached to a base on the seabed by means of an articulation which allows them some freedom of movement. The section of the structure above water is designed to carry the drilling rig, or production rigs for wells already drilled.

Such structures are increasingly useful, but they raise certain problems. There are difficulties in hammering off-axis, for wells with the axis off-center in relation to the drilling structure, and in shifting the drilling rig on the structure. Production wells also haveto be kept waiting until the final phase of drilling, or the rig immobilized while wells already in production are being inspected.

The present invention offers a way of overcoming such problems, by providing an off-centering device which allows the articulated structure to revolve or move transversely in relation to the base. In particular, this device allows multiple wells to be drilled in a circle by the central part of the structure. When drilling is over, the structure can be moved back to the center of the site, allowing direct access to wells already drilled and installed, for servicing or inspection.

The off-centering device as in the invention, linking a base on the seabed to the articulation of an abovewater articulated structure, consists of a roller-table on the base, surmounted by a vertical pivot-shaft, a circular roller-path, also on the base and concentric with the pivot, an off-centering carriage that can revolve round the pivot, supported by the roller-path and roller-table, with a guide-ramp on top, along which the lower end of the main articulation of the structure can slide, and means of rotating the carriage and sliding the articulated structure along the guide-ramp on top of it.

The carriage has an opening through which the components of a drilling or servicing wellhead can pass.

In one embodiment of the device, the means of rotating the carriage consist of a rack alongside the rollerpath, a device on the off-centering carriage with wheels or rollers, which run on the roller-path, and a displacement system incorporated in the carriage and resting on the rack.

In one embodiment, the system consists of one or more double-action end jacks on the carriage, operating blocks which fit into the slots in the rack, acting as stops.

In another embodiment, the system consists of one or more double-action end jacks on the carriage, operating self-blocking ratchets which engage in the rack.

Another type of system that may be used consists of a hydraulic motor on the off-centering carriage, driving a pinion which engages with the rack.

Although a wheel or roller system is recommended for the carriage, other systems performing equivalent functions also come within the framework of the inventron.

In another embodiment the system for sliding the articulated structure along the guide-ramp consists of a rack alongside the ramp, a device on the lower end of the main articulation of the structure, with wheels or rollers which run on the ramp, and a displacement system on the lower end of the articulation, resting on the rack.

This displacement system is preferably similar to those for rotating the off-centering carriage, as described above, although other equivalent systems also come within the framework of the invention.

In one recommended embodiment, the pivot-shaft on the roller-table contains effluent pipes, consisting of one passage for the supply of production-well effluents andanother for their removal.

The invention is illustrated by, without being confined to, the following description of one off-centering device for an articulated drilling and production structure, as shown in the accompanying figures.

FIG. 1 is a diagrammatic side view of the articulated structure, off-centering device and base.

FIG. 2 is a schematic section view of the installation FIG. 1, taken along the line II-lI of FIG. 1, looking downward.

FIG. 3 is a schematic section view of the offcentering device fitted to the base, taken along the line III--III of FIG. 1 looking downward.

The base (I), resting on the seabed (26), is of standard type, constructed to suit the individual features of the site. It is designed to take a number of drilling or servicing wellheads, which are passed through and, once installed, are protected by the base. There is a circular roller-path (2) with parallel rack, on the top of this base, allowing the drilling zone to be covered, and a roller-table (3), surmounted by a vertical pivot-shaft (4), concentric with the roller-path. The pivot has two separate central passages, for the effluent produced by the well and sent to the treatment installation, and for removal of the treated effluent. One of these passages is linked with the pipes (5) connected to the underwater manifolds (6), and the other to the pipe (7) by which production is removed after treatment. The pivot also acts as a link for the remote controls (8) for the under-water installations.

An off-centering carriage (9) rests on the base (1). It can revolve on the roller-path (2) and roller-table (3), by means of a system with coupled, superimposed wheels (10), to prevent loss of balance during movement.

There is a wide opening in this carriage, to allow drilling or servicing wellhead components to pass through.

The carriage is moved by means of double-action end jacks (11), hydraulically controlled from the surface, and operating blocks which fit into the slots in the rack alongside the roller-path.

The top of the off-centering carriage slopes slightly, and has a guide-ramp (12), with a rack.

The lower end (13) of the main articulation (14) of the structure fits on to this guide-ramp, and is made to slide along it by jacks (15), which also operate blocks fitting into the slots in the rack along the ramp, causing the whole articulated structure to move transversely.

The articulated structure (16) contains a number of passages (17) in a circle round its axis, with exactly the same diameter as the circle of wells on the base (1).

These passages can be used to insert tubes (18), when instruments need to be installed. This is not possible until the final phase of drilling has been reached and the articulated structure has returned to its original position and is no longer off-center, so that each passage (17) corresponds to a well installed on the base.

The structure also contains one passage (19) with a larger diameter than the others, which in the off-center or drilling position, is in alignment with the pivot-shaft (4). Two coupled pipes (20) can be inserted in this passage and connected to the corresponding passages in the pivot, to convey the effluent from production wells to the treatment plant at the upper end of the structure, and remove the treated effluent. The remote-control lines (8) for the wellhead installations and jacks also pass through it.

The articulated structure also contains a central passage (21), running through the whole installation, including the articulation (14). This passage is large enough to accomodate drilling wellheads, so that they can be installed in the base.

Two equipment passages (22) are also provided for installation operations on well during the drilling of subsequent wells, or to allow a diving bell to pass.

The part (24) of the articulated structure above the surface (25) has all the drilling equipment on separate levels, away from the well-access passages (17). Production installations are isolated from drilling installations, to ensure complete safety.

The installation according to the invention is installed and operated briefly as follows.

The articulated structure (16) is towed out to the site, positioned, and attached in the standard way to the off-centering carriage (9), previously installed on the base (1). The structure is then in the centre of the installation.

Jacks (l), controlled from the surface, slide the structure transversely along the guide-ramp (12) on the off-centering carriage, to an end position, corresponding to the radius of the circle of wells to be drilled. Other jacks (11) then take over, moving the carriage round the pivot-shaft (4), to position the articulated structure over the spot chosen for drilling.

In order to avoid placing too great a strain on the jacks, by making them move such a mass, the vertical stress at the level of the articulation can be adjusted by de-ballasting the articulated structure. This is done only while the structure is being moved. Once positioned, it is again stabilized.

Throughout drilling operations, wells already drilled and equipped can be brought into production by means of the effluent passages in the pivot-shaft (4).

When multicircular drillings are completed, the articulated structure is brought back to its original position in the centre of the installation.

From this position, without further movement, the wells can be reached through the passages in the structure (l7 using light equipment for various instrument operations.

The articulated structure used for drilling can also be replaced, once drilling is completed, by an articulated structure designed solely for hydrocarbon production and treatment, and repairs to defective wells.

The pivot-shaft (4) in the off-centering device allows the articulated structure to be changed with complete safety, and its design ensures total protection of wellheads during the operation.

What is claimed is:

1. A device for mounting a structure which projects above the water in an eccentric position with respect to an underwater base, said device comprising a carriage,

means supporting said carriage for rotation on said base about a vertical shaft which is located centrally of said base but eccentrically of said carriage, means supporting said structure on said carriage for transverse movement relative to said shaft, and means for rotating said carriage on said base and for moving said structure on said carriage.

2. A device as claimed in claim 1, in which said carriage has an opening therein through which an article lowered from said structure can pass to reach said base.

3. A device as claimed in claim 1 in which said structure comprises two parts articulated to each other.

4. A device as claimed in claim 1 in which said structure contains a central vertical passage and a plurality of additional passages arranged in a circle centered on said central passage.

5. A device as claimed in claim 4 in which said structure supporting means is a ramp positioned to permit movement of said structure between a position in which said central vertical passage is in alignment with the vertical shaft on said base and a position in which one of said additional passages is so aligned.

6. A device as claimed in claim 1 in which said carriage-supporting means comprises a circular roller-path on said base and a plurality of rollers mounted to roll on said path between said base and carriage.

7. A device as claimed in claim 6 in which said means for rotating said carriage on said base comprises a rack parallel to said roller path and power means carried by said structure for actuating drive means engaging said rack.

8. A device as claimed in claim 7 in which said power means comprises at least one jack.

9. A device as claimed in claim 1 in which the means for moving said structure on said carriage comprises a rack and power means which actuates drive means cooperating with said rack. 

1. A device for mounting a structure which projects above the water in an eccentric position with respect to an underwater base, said device comprising a carriage, means supporting said carriage for rotation on said base about a vertical shaft which is located centrally of said base but eccentrically of said carriage, means supporting said structure on said carriage for transverse movement relative to said shaft, and means for rotating said carriage on said base and for moving said structure on said carriage.
 2. A device as claimed in claim 1, in which said carriage has an opening therein through which an article lOwered from said structure can pass to reach said base.
 3. A device as claimed in claim 1 in which said structure comprises two parts articulated to each other.
 4. A device as claimed in claim 1 in which said structure contains a central vertical passage and a plurality of additional passages arranged in a circle centered on said central passage.
 5. A device as claimed in claim 4 in which said structure supporting means is a ramp positioned to permit movement of said structure between a position in which said central vertical passage is in alignment with the vertical shaft on said base and a position in which one of said additional passages is so aligned.
 6. A device as claimed in claim 1 in which said carriage-supporting means comprises a circular roller-path on said base and a plurality of rollers mounted to roll on said path between said base and carriage.
 7. A device as claimed in claim 6 in which said means for rotating said carriage on said base comprises a rack parallel to said roller path and power means carried by said structure for actuating drive means engaging said rack.
 8. A device as claimed in claim 7 in which said power means comprises at least one jack.
 9. A device as claimed in claim 1 in which the means for moving said structure on said carriage comprises a rack and power means which actuates drive means cooperating with said rack. 